Pinch leg from the back (3)
I believe the answer is:
nip
'pinch' is the definition.
(nip can mean to pinch or bite)
'leg from the back' is the wordplay.
'leg' becomes 'pin' (pin is a kind of leg).
'from the back' says the letters should be written backwards.
'pin' back-to-front is 'NIP'.
(Other definitions for nip that I've seen before include "Pinch sharply, perhaps in the bud" , "Pinch, short drink" , "A small whisky" , "Swift bite" , "pop and > have a bite" .)